Surge diverters (also called overvoltage protectors) including a λ/4 short-circuit line are generally known. In the center frequency of the fundamental frequency band, the λ/4 line transforms the short-circuit line at its end into an idle state at its beginning. One advantage of this type of diverter is that they do not generate any intermodulation signals. A disadvantage of these diverters, however, is that no supply direct voltage can be transmitted via the coaxial line in the course of which the surge diverter is situated, which is a result of the electric connection between the inner conductor and the outer conductor of the surge diverter by the λ/4 short-circuit line.
U.S. Pat. Nos. 6,101,080 and 6,456,478 (both to Kuhne) disclose a coaxial surge diverter in which the end of the inner conductor of a short-circuit line is connected with its outer conductor via a concentrated capacitor dimensioned in such a way that the inner conductor and the outer conductor of the short-circuit line act in the fundamental frequency band as a transforming λ/4 short-circuit line. A gas discharge device is arranged parallel to the capacitor which ignites at a certain surge value. Because the outer conductor and the inner conductor of the coaxial line sections are electrically isolated from each other in normal operation, direct voltages or low-frequency alternating voltages can additionally be transmitted via a coaxial line containing this surge diverter. The gas discharge device is located in the HF field at the end of the short-circuit line, which leads to the consequence that the discharge path can be pre-ionized at least in the transmission of high HF outputs. This typically leads to of the production of intermodulation products, as well as to an undesirable reduction of the igniting voltage value. The contact between the inner conductor of the short-circuit line and its outer conductor (via the capacitor), moreover, describes the use of frequency ranges above approximately 1 GHz because a sufficient capacitance cannot be realized due to very limited space for lower frequencies by taking into account the surge impedance to be maintained.
Another type of surge diverter is disclosed in U.S. Pat. No. 6,529,357 (Landinger et al). In this diverter, the inner conductor of the λ/4 short-circuit line is arranged in a chamber formed in the outer conductor of the coaxial line section and is electrically in contact at its end with the outer conductor.